Servicing procedure for single-stage mixed fluid/gas shock strut

ABSTRACT

Methods for servicing shock struts are provided. In various embodiments, a method for servicing a shock strut may comprise deflating the shock strut; compressing the shock strut until the shock strut is in a fully compressed position; and charging the shock strut with a liquid until a pressure of the liquid decreases a volume of a residual air located inside of the shock strut. In various embodiments, charging the shock strut with liquid under pressure may reduce the volume of trapped air inside of the shock strut to a negligible volume, eliminating the servicing variations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, and thebenefit of U.S. patent application Ser. No. 14/934,741, filed on Nov. 6,2015, and entitled “SERVICING PROCEDURE FOR SINGLE-STAGE MIXED FLUID/GASSHOCK STRUT” which is incorporated by reference herein in its entirety.

FIELD

The present disclosure relates to landing gear, and more particularly,to systems and methods for increasing the serviceability of shock strutswithin landing gear.

BACKGROUND

Functionality and performance of a landing gear shock strut depends onits gas pressure and oil volume. Often, a shock strut assembly featuresa piston that compresses a fluid within a sealed chamber. The fluidtypically includes a gas segment and a liquid segment. To this end,shock struts may be serviced with gas and hydraulic fluid on a regularbasis to compensate for normal gas and oil leakage during operation.With typical single stage shock struts, the aircraft is lifted above theground so that the shock strut can be cycled multiple times in attemptto fully remove any trapped gas internal to the shock strut duringservicing. This can be time consuming, cumbersome, and/or costly.

SUMMARY

Methods for servicing a shock strut are provided. A method for servicinga shock strut may comprise: deflating the shock strut; compressing theshock strut until the shock strut is in a fully compressed position; andcharging the shock strut with a liquid until a pressure of the liquiddecreases a volume of a residual air located inside of the shock strut.

In various embodiments, the method may further comprise increasing thepressure of the liquid until a shock strut piston reaches apre-determined extension. The method may further comprise charging theshock strut with a gas. The method may further comprise discharging apre-determined volume of liquid from the shock strut. The shock strutmay include a first valve and a second valve. The compressing may beperformed via at least one of a jack or a weight of a vehicle, thevehicle supported at least in part by the shock strut. The method mayfurther comprise lowering the jack until a shock strut piston is in afully extended position.

A method for weight on wheel shock strut servicing may comprise:deflating the shock strut until the shock strut is in a fully compressedposition; charging the shock strut with an oil until a pressure of theoil decreases a volume of a residual air located inside of the shockstrut; and charging the shock strut with a gas until the gas comprises apre-determined pressure.

In various embodiments, the charging the shock strut with the oil maycomprise pumping the oil into a second valve and closing a first valvein response to the oil exiting the shock strut via the first valve. Thedeflating may comprise releasing the gas from the shock strut, wherein aweight of a vehicle, supported at least in part by the shock strut,compresses the shock strut. The pre-determined pressure may bedetermined, at least in part, based upon a servicing temperature. Themethod may further comprise increasing the pressure of the oil until ashock strut piston reaches a pre-determined extension. Thepre-determined extension may be determined, at least in part, based upona servicing temperature. The method may further comprise discharging apre-determined volume of oil from the shock strut. The pre-determinedvolume of oil may be determined, at least in part, based upon aservicing temperature.

A method for weight off wheel shock strut servicing may comprise:deflating the shock strut; compressing the shock strut via a jack untilthe shock strut is in a fully compressed position; charging the shockstrut with an oil until a pressure of the oil reduces a volume of aresidual air located inside of the shock strut; lowering the jack untila shock strut piston reaches a pre-determined extension; and chargingthe shock strut with a gas until the gas comprises a pre-determinedpressure.

In various embodiments the charging the shock strut with the oil maycomprise pumping the oil into a second valve and closing a first valvein response to the oil exiting the shock strut via the first valve. Thedeflating may comprise releasing the gas from the shock strut. Thepre-determined pressure may be determined, at least in part, based upona servicing temperature. The pre-determined extension may be determined,at least in part, based upon a servicing temperature.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIG. 1 illustrates, in accordance with various embodiments, a singlestage shock strut for use in landing gear of an aircraft;

FIG. 2A illustrates, in accordance with various embodiments, a schematicview of a shock strut in a fully compressed position during a weight onwheel oil servicing procedure including filling a strut with oil;

FIG. 2B illustrates, in accordance with various embodiments, a schematicview of a shock strut in a fully compressed position during a weight onwheel oil servicing procedure including charging a strut withpressurized oil;

FIG. 2C illustrates, in accordance with various embodiments, a schematicview of a shock strut in a fully compressed position during a weight onwheel servicing procedure according to procedure #2 of the servicingchart in FIG. 3;

FIG. 2D illustrates, in accordance with various embodiments, a schematicview of a shock strut extended to a pre-determined position during aweight on wheel gas servicing procedure including charging a strut withgas;

FIG. 2E illustrates, in accordance with various embodiments, a schematicview of a shock strut extended to a pre-determined position during aweight on wheel servicing procedure according to procedure #1 of theservicing chart in FIG. 3;

FIG. 3 illustrates, in accordance with various embodiments, a shockstrut oil servicing chart;

FIG. 4 illustrates, in accordance with various embodiments, a shockstrut gas servicing chart;

FIG. 5A illustrates, in accordance with various embodiments, a schematicview of a shock strut in a fully compressed position during a weight offwheel servicing procedure according to procedure #2 of the servicingchart in FIG. 3;

FIG. 5B illustrates, in accordance with various embodiments, a schematicview of a shock strut in a fully extend position during a weight offwheel gas servicing procedure;

FIG. 5C illustrates, in accordance with various embodiments, a schematicview of a shock strut extended to a pre-determined position during aweight off wheel servicing procedure according to procedure #1 of theservicing chart in FIG. 3;

FIG. 6 illustrates, in accordance with various embodiments, a method forweight on wheel servicing of a shock strut; and

FIG. 7 illustrates, in accordance with various embodiments, a method forweight off wheel servicing of a shock strut.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration and their best mode. While these exemplary embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the disclosure, it should be understood that other embodimentsmay be realized and that logical, chemical and mechanical changes may bemade without departing from the spirit and scope of the disclosure.Thus, the detailed description herein is presented for purposes ofillustration only and not of limitation. For example, the steps recitedin any of the method or process descriptions may be executed in anyorder and are not necessarily limited to the order presented.Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact.

Aircraft landing gear systems in accordance with the present disclosuremay comprise a shock strut. A shock strut may comprise various fluidssuch as oil and gas. Performance of the shock strut may be evaluated bymonitoring aspects of the shock strut, including gas temperature, gaspressure, oil pressure, and stroke of the shock strut at various pointsduring operation of the aircraft. Stroke may refer to a shock strutpiston position. Servicing of a shock strut may be performed weight onwheel or weight off wheel or also a combination of weight on wheel andweight off wheel. Weight on wheel service refers to the servicing of ashock strut when the weight of a vehicle, such as an aircraft, issupported by the vehicles wheel assembly via at least one shock strut onthe ground. Weight off wheel service refers to the servicing of a shockstrut when the weight of a vehicle, such as an aircraft, is notsupported by the vehicles wheel assembly via at least one shock strut onthe ground. In the case of weight off wheel, the vehicles weight may besupported by the frame of the vehicle, such as an aircraft wing, forexample.

Accordingly, with reference to FIG. 1, a landing gear assembly 100 isillustrated. In various embodiments, landing gear assembly 100 comprisesa shock strut 104. Shock strut 104 may be mechanically coupled to awheel assembly 106. In various embodiments, shock strut 104 may beconfigured to absorb and dampen forces transmitted by wheel assembly 106to an aircraft.

Shock strut 104 may comprise, for example, a piston 102 and a cylinder108. Cylinder 108 may be configured to receive piston 102 in a mannerthat allows the two components to telescope together and absorb anddampen forces transmitted by wheel assembly 106.

In various embodiments, a liquid, such as hydraulic fluid or an oil, islocated within cylinder 108. Cylinder 108 and piston 102 may, forexample, be configured to seal such that liquid contained withincylinder 108 is prevented from leaking as piston 102 translates relativeto cylinder 108. Further, cylinder 108 may be configured to contain agas or air. Shock strut 104 may comprise a proximal end and a distalend, wherein the distal end is opposite the proximal end, the distal endbeing the end of the shock strut closest to a wheel or wheel assembly ofa vehicle, such as wheel assembly 106, for example. The air may bepositioned above the oil (referred to as an “air-over-oil” arrangement)or vice versa, where the term “above” in this context means in thedirection of the proximal end of the shock strut. Similarly, cylinder108 and piston 102 may be sealed such that gas and oil is prevented fromleaking as piston 102 moves relative to cylinder 108. As such, shockstrut 104 may comprise a pressurized environment within cylinder 108.

Shock strut 104 may further comprise, for example, a gas pressure sensor110. In various embodiments, gas pressure sensor 110 may be capable ofmeasuring the pressure of the gas within shock strut 104 at a desiredtime. For example, gas pressure sensor 110 may measure the gas pressurewithin shock strut 104 before, during, or after take-off, or at anypoint during the duty cycle of shock strut 104.

In various embodiments, shock strut 104 may further comprise, forexample, a gas temperature sensor 112. Gas temperature sensor 112 may becapable of measuring the temperature of the gas within shock strut 104at any point during the duty cycle of shock strut 104.

Similarly, shock strut 104 may comprise an oil pressure sensor 114. Invarious embodiments, oil pressure sensor 114 may be capable of measuringthe pressure of the oil within shock strut 104 at a desired time. Forexample, oil pressure sensor 114 may measure the oil pressure withinshock strut 104 at any point during the duty cycle of shock strut 104.

In various embodiments, shock strut 104 may include various othersensors. Shock strut 104 may include a temperature sensor. A temperaturesensor may be used to measure the temperature of oil inside of shockstrut 104.

Shock strut 104 may also comprise a position sensor 116. In variousembodiments, position sensor 116 may be capable of measuring theposition of piston 102 relative to cylinder 108, which is conventionallyreferred to as the stroke or stroke, of shock strut 104 at a desiredtime. Position sensor 116 may be configured to measure the positionindirectly, for example, by measuring the orientation of one or moreshock strut torque links 118 (or other components). For example,position sensor 116 may measure the stroke of shock strut 104 at anypoint during the duty cycle of shock strut 104.

With respect to FIG. 2B through FIG. 2E, elements with like elementnumbering, as depicted in FIG. 2A, are intended to be the same and willnot necessarily be repeated for the sake of clarity.

With reference to FIG. 2A, a schematic view of a shock strut (alsoreferred to herein as a single stage shock strut) 200 is illustrated ina fully compressed position. In various embodiments, shock strut 210 maybe similar to shock strut 104 (see FIG. 1). In various embodiments,shock strut 210 may include piston 202 and cylinder 204. In variousembodiments, cylinder 204 may be configured to receive piston 202 in amanner that allows the two components to telescope together and absorband/or dampen forces transmitted by wheel assembly 206.

In various embodiments, shock strut 210 may include a gascharge/dis-charge valve (also referred to herein as a first valve) 212.In various embodiments, gas charge/discharge valve 212 may be used todischarge gas from inside of shock strut 210. In various embodiments,gas charge/discharge valve 212 may be used to charge gas into shockstrut 210. In various embodiments, gas charge/discharge valve 212 may beused to charge and/or discharge oil into shock strut 210. In variousembodiments, shock strut 210 may include an oil charge/discharge valve(also referred to herein as a second valve) 214. In various embodiments,oil charge/discharge valve 214 may be used to charge oil into shockstrut 210. In various embodiments, oil charge/discharge valve 214 may beused to discharge oil from shock strut 210. Although shock strut 210 isdescribed herein as a shock strut comprising two charge/discharge valves212, 214, the methods as described herein may be performed on a shockstrut having a single valve. For example, an adaptor with two ports maybe connected to a single valve of shock strut 210, wherein one of theports is connected to an oil pump and the other port is connected to acharged gas cylinder.

With momentary reference to FIG. 6 a method for weight on wheelservicing of a shock strut is provided, in accordance with variousembodiments.

In various embodiments, a weight on wheel shock strut servicingprocedure 200 may be performed. Weight on wheel shock strut servicingprocedure 200 may include an oil servicing procedure followed by a gasservicing procedure. In various embodiments, weight on wheel shock strutservicing procedure 200 may begin by deflating the shock strut 210 (Step602) such that it is in a fully compressed position as illustrated inFIG. 2A. Shock strut 210 may be deflated by removing gas from inside ofshock strut 210 via gas charge/discharge valve 212. Stated another way,shock strut 210 may be deflated by opening gas charge/discharge valve212. However, shock strut 210 may be deflated via any suitable method.The weight of a vehicle, such as an aircraft for example, may compressshock strut 210 into a fully compressed position when servicing isperformed weight on wheel. A first hose 216 may be coupled to gascharge/discharge valve 212. In various embodiments, first hose 216 maybe a transparent hose. In various embodiments, any air pockets locatedin oil flowing through first hose 216 may be visible through first hose216. A second hose 218 may be coupled to the oil charge/discharge valve214. The second hose 218 may be coupled to an oil pump 220 (see FIG.2B). Hydraulic fluid (also referred to herein as oil) may be pumped intothe shock strut 210. Oil may be pumped into shock strut 210 until oilstarts to flow out of the shock strut through first hose 216 as shown atarrow 224. Thus, oil may be cycled through shock strut 210, wherein oilenters shock strut 210 via the oil charge/discharge valve 214 and exitsshock strut 210 via gas charge/discharge valve 212. Oil flowing out offirst hose 216 may be captured in a container 222 as shown at arrow 224.Gas charge/discharge valve 212 may be closed in response to oilbeginning to flow out first hose 216. Accordingly, shock strut 210 maybe filled with oil.

With reference to FIG. 2B, weight on wheel shock strut servicingprocedure 200 of shock strut 210 may be continued by monitoring shockstrut 210 internal pressure. As illustrated in FIG. 2B, pressure ismonitored by attaching a pressure gauge 230 to charge/discharge valve212. However, it is contemplated that shock strut 210 internal pressuremay be measured using any suitable method. For example, shock strut 210may be equipped with a gas pressure transducer which may monitor shockstrut pressure. Thus, pressure gauge 230 may not be used in someinstances. In various embodiments, pressure gauge 230 may be located atcharge discharge valve 214 or at oil pump 220.

In various embodiments, a servicing temperature may be measured. Theservicing temperature may be the ambient temperature. An operator ortechnician may determine an oil servicing procedure based upon themeasured servicing temperature. In various embodiments, a first orsecond oil servicing procedure may be performed wherein the first oilservicing procedure involves the shock strut extending during the oilservicing procedure and the second oil servicing procedure involves theshock strut remain fully compressed or retracted during the oilservicing procedure. What follows is a description of a second oilservicing procedure followed by the gas servicing procedure whichconcludes a weight on wheel shock strut servicing procedure, inaccordance with various embodiments. Then, a first oil servicingprocedure is described with reference to FIG. 2E, in accordance withvarious embodiments.

With momentary reference to FIG. 3, a service chart 300 may be provided.Service chart 300 may indicate to a technician the type of oil servicingprocedure to use depending on the servicing temperature. For example, asillustrated in FIG. 2B, if the servicing temperature were negativetwenty degrees Celsius (−20° C.) (−4° F.), then service chart 300 mayindicate to a technician to use procedure #2 (also referred to herein asa second oil procedure).

In various embodiments, with gas charge/discharge valve 212 closed, oilmay be pumped into shock strut 210 via oil charge/discharge valve 214 atpressure (see step 603). In various embodiments, oil may be pumped intoshock strut 210 via gas charge/discharge valve 212. Oil may be pumpedinto shock strut 210 until the internal pressure of the oil inside ofshock strut 210 is large enough to crush any pockets of air (alsoreferred to herein as residual air) located inside of shock strut 210but not large enough to extend shock strut 210. Accordingly, the volumeof any residual air inside of shock strut 210 may be reduced to anegligible volume. In various embodiments, a negligible volume may bedefined as having reduced the volume of residual air inside of the shockstrut 210 by at least ten times. Thus, the pressure of the oil inside ofthe shock strut may be increased. Stated another way, shock strut 210may be filled with pressurized oil. For example, oil may be pumped intoshock strut 210 until the internal pressure of shock strut 210 reachesbetween 100 and 150 psig (689.48-1034.21 kPa). Next, oilcharge/discharge valve 214 may be closed and second hose 218 removed.The internal pressure of shock strut 210 may be recorded and, ifapplicable, pressure gauge 230 may be removed. This may complete the oilservicing procedure.

With reference to FIG. 2C, a gas servicing procedure may be performedaccording to procedure #2 of servicing chart (see FIG. 3) following theoil servicing procedure. A compressed gas tank 236 may be coupled to gascharge/discharge valve 212. In various embodiments, compressed gas tank236 may contain a gas such as nitrogen. However, it is contemplated thatany suitable gas may be contained by compressed gas tank 236. In variousembodiments, compressed gas tank 236 may be coupled to gascharge/discharge valve 212 via a hose (also referred to herein as a gascharging hose) 238 or any other suitable method. In various embodiments,gas charging hose 238 may be pressurized to a pressure which is greaterthan the internal pressure of the shock strut before opening gascharge/discharge valve 212 in order to avoid back flow of oil when gascharge/discharge valve 212 is opened. In various embodiments, the gascharge/discharge valve 212 may be opened to maintain pressure inside ofshock strut 210.

In various embodiments, with shock strut 210 in a fully compressedposition, a variable valve 232 may be coupled to oil charge/dischargevalve 214. In various embodiments, variable valve 232 may compriseground support equipment (GSE). In various embodiments, variable valve232 may comprise a valve with a variable restriction flow path such thata flow rate of a fluid flowing through variable valve 232 may be variedin a controlled manner. In various embodiments, a measuring element 234may be used during the gas servicing procedure. In various embodiments,measuring element 234 may comprise a graduated container or the like formeasuring the volume of a fluid. The technician may use the variablevalve 232 to drain or discharge a pre-determined volume of oil fromshock strut 210 (see step 604) into measuring element 234 according toservice chart 300 (see FIG. 3). Continuing with the example of aservicing temperature of −20° C., the technician may drain sixteen cubicinches (16 in³) (262.19 cm³) from shock strut 210 into measuring element234. Thus, shock strut 210 may be filled with a desired amount of oil.The variable valve 232 may then be removed and oil charge/dischargevalve 214 closed and capped.

With reference to FIG. 2D, a continuation of the gas servicing procedureis illustrated. With the desired amount of oil inside of shock strut210, the gas servicing procedure may continue by charging or inputtinggas from compressed gas tank 236 into shock strut 210 via gascharge/discharge valve 212. Accordingly, gas may be charged into shockstrut 210 until the internal pressure of shock strut 210 counteracts theweight of a vehicle supported by shock strut 210 and the shock strut 210extends. With further reference to FIG. 4, gas may be charged into shockstrut 210 (see step 606) until the internal pressure “P2” of shock strut210 and the extension dimension “X2” of shock strut 210 match thereference curves 402 at the servicing temperature as initially used inservice chart 300 (see FIG. 3). Thus, FIG. 4 illustrates internalpressure “P2” and extension dimension “X2” matching the reference curves402 at the servicing temperature of −20° C. In various embodiments, thismay determine that weight on wheel shock strut servicing procedure 200is appropriate.

With reference to FIG. 2E, during weight on wheel shock strut servicingprocedure 200 the servicing temperature may be such that service chart300 (see FIG. 3) indicates to a technician to use Procedure #1 (alsoreferred to herein as a first oil procedure). For example, if theservicing temperature is 50° C., service chart 300 may indicate to useprocedure #1. In various embodiments, procedure #1 may include pumpingoil into shock strut 210 until the internal pressure counter acts theweight of a vehicle supported by shock strut 210 and piston 202 extendsto extension “X1” (also referred to herein as a pre-determinedextension) as illustrated in FIG. 2E (see step 605). For example, if theservicing temperature is 50° C., then according to service chart 300 ofFIG. 3, oil may be pumped into shock strut 210 until piston 202 extendsto an extension “X1” of 0.5″. Thus, a greater volume of oil may bepumped into shock strut 210 in procedure #1 than in procedure #2 asdescribed herein. This may compensate for thermal expansion of the oilat higher temperatures. Accordingly, shock strut 210 may be filled witha desired volume of oil. Next, as previously mentioned oilcharge/discharge valve 214 may be closed and second hose 218 removed.The internal pressure of shock strut 210 may be recorded and, ifapplicable, pressure gauge 230 may be removed. This may complete the oilservicing procedure. The gas servicing procedure may then continue aspreviously described in FIG. 2D in regards to weight on wheel shockstrut servicing procedure 200.

With respect to FIG. 5A through FIG. 5C, elements with like elementnumbering, as depicted in FIG. 2A through FIG. 2E, are intended to bethe same and will not be repeated for the sake of clarity.

A second oil servicing procedure is described followed by a gasservicing procedure which concludes a weight off wheel shock strutservicing procedure, in accordance with various embodiments. Then, afirst oil servicing procedure is described in FIG. 5C, in accordancewith various embodiments.

With reference to FIG. 5A, a weight off wheel shock strut servicingprocedure 500 may be performed, in accordance with various embodiments.Weight off wheel shock strut servicing procedure 500 may include an oilservicing procedure followed by a gas servicing procedure. In variousembodiments, weight off wheel shock strut servicing procedure 500 may besimilar to weight on wheel shock strut servicing procedure 200.

With momentary reference to FIG. 7 a method 700 for weight off wheelservicing of a shock strut is provided, in accordance with variousembodiments.

In various embodiments, weight off wheel shock strut servicing procedure500 may begin by deflating the shock strut 210 (see step 702) in asimilar manner as described in weight on wheel shock strut servicingprocedure 200. However, the weight of a vehicle, such as an aircraft forexample, may be supported by means other than the wheel assembly 206.Thus, a jack 552 may be used to compress shock strut 210 into a fullycompressed position as illustrated in FIG. 5A (see step 703).

As described herein, with momentary reference to FIG. 3, a service chart300 may be used to determine if a first or second oil servicingprocedure should be used to service shock strut 210 according to theservicing temperature. In the event that it is determined that procedure#2 should be used, oil may be pumped into shock strut 210 in a similarmanner as described in weight on wheel shock strut servicing procedure200 until the internal pressure of the oil inside of shock strut 210 islarge enough to crush any pockets of air (also referred to herein asresidual air) located inside of shock strut 210 but not large enough toextend shock strut 210 (see step 704). For example, oil may be pumpedinto shock strut 210 until the internal pressure of shock strut 210reaches between 100 and 150 psig (689.48-1034.21 kPa). Next, oilcharge/discharge valve 214 may be closed and second hose 218 removed.The internal pressure of shock strut 210 may be recorded and, ifapplicable, pressure gauge 230 may be removed. This may complete the oilservicing procedure. Similar to weight on wheel procedure, following theoil servicing procedure, a compressed gas tank 236 may be coupled to gascharge/discharge valve 212 and a variable valve 232 (see FIG. 2C) may beused to drain or discharge a pre-determined volume of oil from shockstrut 210 (see step 705) into measuring element 234 (see FIG. 2C)according to service chart 300 (see FIG. 3) while oil remainspressurized by the gas tank 236 (see FIG. 5B).

With reference to FIG. 5B, a gas servicing procedure is illustrated, inaccordance with various embodiments, for a weight off wheel shock strutservicing procedure 500. In various embodiments, gas may then be chargedinto shock strut 210 via compressed gas tank 236. Jack 552 may then beslowly lowered while gas is charged into shock strut 210 until shockstrut 210 is in a fully extended position as illustrated in FIG. 5B (seestep 707). Shock strut 210 may comprise an extension dimension “X_(max)”(also referred to herein as a pre-determined extension) when shock strut210 is in a fully extended position. Gas may continue to be charged intoshock strut 210 until the internal pressure of shock strut 210 reaches avalue that corresponds to the reference curves 402 given in servicingchart 400 (see FIG. 4) corresponding to the servicing temperature and anextension of “X_(max)” (see step 708). When the desired pressure isreached, gas charge/discharge valve may be closed and the compressed gastank removed from shock strut 210.

With reference to FIG. 5C, procedure #1 (see FIG. 3) for weight offwheel shock strut servicing procedure 500 is described, in accordancewith various embodiments. Oil may be pumped into shock strut 210 via oilcharge/discharge valve 214 until the internal pressure of shock strut210 is large enough to crush any pockets of residual air located insideof shock strut 210 but not large enough to extend shock strut 210. Next,while oil pressure is maintained by pumping oil into shock strut 210,jack 552 may be slowly lowered until piston 202 has extended to apre-determined extension “X1” according to service chart 300 (see FIG.3) (see step 706). Next, oil charge/discharge valve 214 may be closedand second hose 218 removed. The internal pressure of shock strut 210may be recorded and, if applicable, pressure gauge 230 may be removed.This may complete the oil servicing procedure. The gas servicingprocedure may then continue as previously described in FIG. 5B inregards to weight off wheel shock strut servicing procedure 500.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”,“various embodiments”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is intended to invoke 35 U.S.C.112(f) unless the element is expressly recited using the phrase “meansfor.” As used herein, the terms “comprises”, “comprising”, or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, article, or apparatus that comprises a list ofelements does not include only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus.

What is claimed is:
 1. A method for servicing a shock strut comprising:deflating the shock strut; compressing the shock strut until the shockstrut is in a fully compressed position; with the shock strut in thefully compressed position, charging the shock strut with a liquid untila pressure of the liquid decreases a volume of a residual air locatedinside of the shock strut; and with the shock strut in the fullycompressed position, discharging a pre-determined volume of liquid fromthe shock strut.
 2. The method of claim 1, further comprising chargingthe shock strut with a gas.
 3. The method of claim 1, wherein the shockstrut includes a first valve and a second valve.
 4. The method of claim1, wherein the compressing is performed via at least one of a jack or aweight of a vehicle, the vehicle supported at least in part by the shockstrut.